The PCIe-DIO-48S/24S is a 48/24 channel PCI Express (PCIe) card designed for use in a variety of digital I/O applications. It uses the high speed PCI Express bus to transfer digital data to and from the card. The digital I/O is compatible with 8255 PPI (mode 0), making it easy to program. This also allows for simple and trouble-free migration from other ACCES PCI digital I/O cards . The card features a x1 lane PCI Express connector which can be used in any available x1, x2, x4, x8, x12, or x16 PCI Express expansion slot. Each 50-pin header has three 8-bit I/O ports designated A, B and C. Port C can be further divided into two 4-bit nibbles. Each port can be programmed as inputs or outputs. Change of State (COS) detection and interrupt capabilities are designed to relieve software from polling routines that can consume valuable processing time. Each port can be programmed for detecting state changes on their lines, in which any changes of the enabled port's bits (low-to-high or high-to-low) will generate an IRQ. An ISR (interrupt service routine) then polls the port to determine which bit changed state and clear the interrupt. The connectors are also compatible with existing 48 and 24 channel ACCES PCI digital I/O cards. One or two flat ribbon cables are routed through a cutout in the mounting bracket and plugged onto the keyed 50-pin male headers on the side of the card. A strain relief bracket securely holds the ribbon cables at the point of exit via the PCIe mounting bracket.